5.3 ZPS of Rh, W, and Re Kink Edges
91
polarize the valence electrons of the edge atoms, which in turn screens and splits the
crystal potential and offsets the entrapped T states in the core band upwardly.
The polarization results in the P component at 30.95 eV. One can estimate the
polarization coefficient with the known energies of the P and the B components, p
= [E 4f7/2 (p) − E 4f7/2 (0)]/[E 4f7/2 (12) − E 4f7/2 (0)] = (30.945–28.889)/2.194 = 93.7%,
which means that the polarization weakens 6.3% the crystal potential experienced
by the 4f electrons in the bulk.
The otherwise T component turns to be T + P with an additional valley at the
bottom edge of the core band because of the coupling of T and P, which follows the
same mechanism for the Rh adatoms and terrace edges. The screening effect also
applies to the trapped states, and therefore, this valley presents, and the T component
becomes P + T. If the C
−1
3 is replaced with pC
−1
3 = C
−1
3.75 , which means that the
original edge states located at z = 3 shift up to energy being equivalent to z =
3.75. The edge bond is strengthened by [E 4f (3.75) − E 4f (0)]/[E 4f (12) − E 4f (0)] =
(31.310−28.889)/2.194 = 1.103, or 10.3%, because of the joint T + P effect.
The ZPS of W edges share the same attributes to those of Rh edges or adatoms [40],
which has been identified as donor-type catalyst. From the electronic configuration
viewpoint, the undercoordinated W edges perform the same to Rh adatoms as donortype catalyst.
DFT calculations on the flat W(110) and the edged W(320) and (540) skins focusing on the local valence DOS evolution [48] verified the BOLS-NEP expectation on
the skin bond contraction and valence charge polarization [48, 50]. DFT calculations
also confirmed the size-reduction induced 4s core band entrapment and the (4d
3 5s
1 )
valence polarization of Mo n clusters. Results in Fig. 5.9 and Table 5.1 confirmed this
expectation.
5.3.4 Re(0001) and (12 ¯
31) Kink Edges
Figure 5.10a shows the ZPS of the original Re (12 ¯
31) 4f 5/2 and 4f 7/2
bands
48,127,227–228,258–261 gained by subtracting the spectrum collected at 0° from
that collected at 75° emission angle after background correction and spectral area
normalization [26, 27, 51–56]. The obvious valleys correspond to the bulk (B) and
peaks to the entrapped kink edges (T). The outermost two atomic layers with the
effective z values of 3.6 (S 2 ) and 2.8 (S 1 ) create the T components, as indicated in
Fig. 5.10b. The small feature at the upper edge of the 4f 7/2 band arises from the 5p 3/2
band overlap of the kinks, instead of polarization.
Figure 5.10b shows the ZPS of the specific 4f 5/2 level. Two valleys centered at
42.645 and 42.910 eV correspond to the B and S 3 components, which indicate that the
B valley contains the S 4 (centered at 42.778 eV) and the S 3 components. Therefore,
the ZPS reveals information of the outermost two atomic layers of the low-index
(12 ¯
31) skin. Except for the valleys, a broad peak at the bottom edge of the 4f 5/2 band
represents the gain of electronic energy when the S 2 and S 1 kinks are involved. The
91
polarize the valence electrons of the edge atoms, which in turn screens and splits the
crystal potential and offsets the entrapped T states in the core band upwardly.
The polarization results in the P component at 30.95 eV. One can estimate the
polarization coefficient with the known energies of the P and the B components, p
= [E 4f7/2 (p) − E 4f7/2 (0)]/[E 4f7/2 (12) − E 4f7/2 (0)] = (30.945–28.889)/2.194 = 93.7%,
which means that the polarization weakens 6.3% the crystal potential experienced
by the 4f electrons in the bulk.
The otherwise T component turns to be T + P with an additional valley at the
bottom edge of the core band because of the coupling of T and P, which follows the
same mechanism for the Rh adatoms and terrace edges. The screening effect also
applies to the trapped states, and therefore, this valley presents, and the T component
becomes P + T. If the C
−1
3 is replaced with pC
−1
3 = C
−1
3.75 , which means that the
original edge states located at z = 3 shift up to energy being equivalent to z =
3.75. The edge bond is strengthened by [E 4f (3.75) − E 4f (0)]/[E 4f (12) − E 4f (0)] =
(31.310−28.889)/2.194 = 1.103, or 10.3%, because of the joint T + P effect.
The ZPS of W edges share the same attributes to those of Rh edges or adatoms [40],
which has been identified as donor-type catalyst. From the electronic configuration
viewpoint, the undercoordinated W edges perform the same to Rh adatoms as donortype catalyst.
DFT calculations on the flat W(110) and the edged W(320) and (540) skins focusing on the local valence DOS evolution [48] verified the BOLS-NEP expectation on
the skin bond contraction and valence charge polarization [48, 50]. DFT calculations
also confirmed the size-reduction induced 4s core band entrapment and the (4d
3 5s
1 )
valence polarization of Mo n clusters. Results in Fig. 5.9 and Table 5.1 confirmed this
expectation.
5.3.4 Re(0001) and (12 ¯
31) Kink Edges
Figure 5.10a shows the ZPS of the original Re (12 ¯
31) 4f 5/2 and 4f 7/2
bands
48,127,227–228,258–261 gained by subtracting the spectrum collected at 0° from
that collected at 75° emission angle after background correction and spectral area
normalization [26, 27, 51–56]. The obvious valleys correspond to the bulk (B) and
peaks to the entrapped kink edges (T). The outermost two atomic layers with the
effective z values of 3.6 (S 2 ) and 2.8 (S 1 ) create the T components, as indicated in
Fig. 5.10b. The small feature at the upper edge of the 4f 7/2 band arises from the 5p 3/2
band overlap of the kinks, instead of polarization.
Figure 5.10b shows the ZPS of the specific 4f 5/2 level. Two valleys centered at
42.645 and 42.910 eV correspond to the B and S 3 components, which indicate that the
B valley contains the S 4 (centered at 42.778 eV) and the S 3 components. Therefore,
the ZPS reveals information of the outermost two atomic layers of the low-index
(12 ¯
31) skin. Except for the valleys, a broad peak at the bottom edge of the 4f 5/2 band
represents the gain of electronic energy when the S 2 and S 1 kinks are involved. The